The present invention broadly relates to a controlled deflection roll or sag-compensating roll having hydrostatic support or pressure or carrier elements and, more specifically pertains to a new and improved construction of a heatable controlled deflection roll.
Generally speaking, the controlled deflection roll of the present invention comprises a stationary support or beam and a roll shell or jacket which is rotatable about the stationary support or beam. The rotatable roll shell or jacket is supported or braced in relation to the stationary support or beam by means of at least one hydrostatic support or carrier or pressure element. This at least one hydrostatic support or carrier or pressure element is displaceable in a pressure space or chamber in radial direction with respect to the stationary support or beam. First supply means are provided for the infeed of a hydraulic pressurized fluid medium to the pressure space or chamber. Furthermore, the at least one hydrostatic support or carrier or pressure element comprises a running surface for the rotatable roll shell or jacket, which running surface faces or confronts the inner side of the rotatable roll shell or jacket and at which running surface there is provided at least one hydrostatic bearing or stabilizing pocket. Second supply means are provided for the infeed of a hydraulic heat carrier medium to the at least one hydrostatic bearing or stabilizing pocket provided at the running surface of the at least one hydrostatic support or carrier or pressure element.
Such heatable or heated controlled deflection rolls, also known in the art as rolls with bending or sag compensation, are known, for example, from Swiss Patent No. 577,598 published July 15, 1976 and U.S. Pat. No. 4,282,639, granted Aug. 11, 1981 and are used, for instance, in smoothing calenders for treating paper webs and setting non-woven fabrics and in plastic material and elastomer calenders for pressure treatment of corresponding material webs at elevated temperatures.
In the controlled deflection roll disclosed in the aforementioned Swiss Patent No. 577,598 the hydrostatic bearing or stabilizing pockets of the hydrostatic support or pressure elements are connected with the pressure chamber of the associated hydrostatic support or pressure element by means of throttle bores or throttle passages. The hydrostatic bearing or stabilizing pockets are thus provided via the pressure chamber with the same hydraulic pressurized fluid medium which serves to generate the pressing force of the hydrostatic support or pressure element by way of the pressure chamber as well as to hydrostatically mount or support the tubular-shaped roll shell or jacket by means of the hydrostatic bearing or stabilizing pockets. For the purpose of heating the tubular-shaped roll shell or jacket, the hydraulic pressurized fluid medium can be heated to the required temperature prior to being supplied to the pressure chambers. In this manner, the tubular-shaped roll shell or jacket of a controlled deflection roll can be heated from within by means of only one single supply of hydraulic pressurized fluid medium to the individual hydrostatic support or pressure elements. However, this is disadvantageous in that the components or devices required for the supply of the hydraulic pressurized fluid medium, for example, pumps, valves or other control units, have to endure the necessarily high temperatures far above 100.degree. C., which temperatures they often cannot withstand. Furthermore, the normally used hydraulic pressurized fluid media, for instance pressure oils, assume such a low viscosity and thus become highly fluid at the required high temperatures, that undesired high leakage occurs.
To avoid the aforesaid disadvantage or shortcoming, efforts have been made to separate the heating of the inner side of the rotatable roll shell or jacket from the supporting, pressing or stabilizing function of the hydrostatic support or pressure element.
It is known, for example, from U.S. Pat. No. 3,997,953, granted Dec. 21, 1976, to provide additional heat-control devices arranged in a row which extends in parallel relationship to the roll axis and is substantially remote from the hydrostatic support or pressure elements. Such heat-control devices guided in the manner of a piston in a borehole or bore are supplied with a heat-control liquid vehicle, while the actual hydrostatic support or pressure elements are supplied with a pressurized fluid medium at a normal temperature.
A controlled deflection roll disclosed, for example, in U.S. Pat. No. 4,282,638, granted Aug. 11, 1981, is equipped with spraying devices arranged in the intermediate space between the stationary support or beam and the rotatable roll shell or jacket. These spraying devices have walls facing the inner surface or side of the rotatable roll shell or jacket. At these walls there are formed openings which, during operation, form liquid jets or streams which impact against the inner surface or side of the rotatable roll shell or jacket. The disadvantage of such heat transfer between the heated oil and the rotatable roll shell or jacket is seen in the fact that additional components and installations are required within the controlled deflection roll and that such components and installations take up space which is often not available, particularly in controlled deflection rolls for high pressing forces, such rolls requiring an especially stable and rigid stationary support or beam.
It is of course known, for example, from U.S. Pat. No. 4,726,691, granted Feb. 23, 1988 to separately supply the pressure chambers and the bearing or stabilizing pockets of a controlled deflection roll with hydraulic pressurized fluid medium. However, the same hydraulic pressurized fluid medium, typically pressure oil, and the same bearing pump are used to supply the pressure oil to the separate delivery or feed lines. Moreover, no heating and thus no heat control liquid vehicle is provided. Even if the hydraulic pressurized fluid medium were heated as known to the art for the purpose of heating the rotatable roll shell or jacket, the same problems, as described hereinbefore, would arise with respect to the sensitiveness to heat of the components as well as of the pressure oil.